drivers/virtio/virtio_balloon.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
   4  * Tosatti's implementations.
   5  *
   6  *  Copyright 2008 Rusty Russell IBM Corporation
   7  */
   8
   9 #include <linux/virtio.h>
  10 #include <linux/virtio_balloon.h>
  11 #include <linux/swap.h>
  12 #include <linux/workqueue.h>
  13 #include <linux/delay.h>
  14 #include <linux/slab.h>
  15 #include <linux/module.h>
  16 #include <linux/balloon_compaction.h>
  17 #include <linux/wait.h>
  18 #include <linux/mm.h>
  19 #include <linux/mount.h>
  20 #include <linux/magic.h>
  21 #include <linux/pseudo_fs.h>
  22
  23 /*
  24  * Balloon device works in 4K page units.  So each page is pointed to by
  25  * multiple balloon pages.  All memory counters in this driver are in balloon
  26  * page units.
  27  */
  28 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  29 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  30 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
  31
  32 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
  33                                              __GFP_NOMEMALLOC)
  34 /* The order of free page blocks to report to host */
  35 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1)
  36 /* The size of a free page block in bytes */
  37 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
  38         (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
  39 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
  40
  41 #ifdef CONFIG_BALLOON_COMPACTION
  42 static struct vfsmount *balloon_mnt;
  43 #endif
  44
  45 enum virtio_balloon_vq {
  46         VIRTIO_BALLOON_VQ_INFLATE,
  47         VIRTIO_BALLOON_VQ_DEFLATE,
  48         VIRTIO_BALLOON_VQ_STATS,
  49         VIRTIO_BALLOON_VQ_FREE_PAGE,
  50         VIRTIO_BALLOON_VQ_MAX
  51 };
  52
  53 enum virtio_balloon_config_read {
  54         VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
  55 };
  56
  57 struct virtio_balloon {
  58         struct virtio_device *vdev;
  59         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
  60
  61         /* Balloon's own wq for cpu-intensive work items */
  62         struct workqueue_struct *balloon_wq;
  63         /* The free page reporting work item submitted to the balloon wq */
  64         struct work_struct report_free_page_work;
  65
  66         /* The balloon servicing is delegated to a freezable workqueue. */
  67         struct work_struct update_balloon_stats_work;
  68         struct work_struct update_balloon_size_work;
  69
  70         /* Prevent updating balloon when it is being canceled. */
  71         spinlock_t stop_update_lock;
  72         bool stop_update;
  73         /* Bitmap to indicate if reading the related config fields are needed */
  74         unsigned long config_read_bitmap;
  75
  76         /* The list of allocated free pages, waiting to be given back to mm */
  77         struct list_head free_page_list;
  78         spinlock_t free_page_list_lock;
  79         /* The number of free page blocks on the above list */
  80         unsigned long num_free_page_blocks;
  81         /*
  82          * The cmd id received from host.
  83          * Read it via virtio_balloon_cmd_id_received to get the latest value
  84          * sent from host.
  85          */
  86         u32 cmd_id_received_cache;
  87         /* The cmd id that is actively in use */
  88         __virtio32 cmd_id_active;
  89         /* Buffer to store the stop sign */
  90         __virtio32 cmd_id_stop;
  91
  92         /* Waiting for host to ack the pages we released. */
  93         wait_queue_head_t acked;
  94
  95         /* Number of balloon pages we've told the Host we're not using. */
  96         unsigned int num_pages;
  97         /*
  98          * The pages we've told the Host we're not using are enqueued
  99          * at vb_dev_info->pages list.
 100          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
 101          * to num_pages above.
 102          */
 103         struct balloon_dev_info vb_dev_info;
 104
 105         /* Synchronize access/update to this struct virtio_balloon elements */
 106         struct mutex balloon_lock;
 107
 108         /* The array of pfns we tell the Host about. */
 109         unsigned int num_pfns;
 110         __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
 111
 112         /* Memory statistics */
 113         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 114
 115         /* To register a shrinker to shrink memory upon memory pressure */
 116         struct shrinker shrinker;
 117 };
 118
 119 static struct virtio_device_id id_table[] = {
 120         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 121         { 0 },
 122 };
 123
 124 static u32 page_to_balloon_pfn(struct page *page)
 125 {
 126         unsigned long pfn = page_to_pfn(page);
 127
 128         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
 129         /* Convert pfn from Linux page size to balloon page size. */
 130         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 131 }
 132
 133 static void balloon_ack(struct virtqueue *vq)
 134 {
 135         struct virtio_balloon *vb = vq->vdev->priv;
 136
 137         wake_up(&vb->acked);
 138 }
 139
 140 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 141 {
 142         struct scatterlist sg;
 143         unsigned int len;
 144
 145         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 146
 147         /* We should always be able to add one buffer to an empty queue. */
 148         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 149         virtqueue_kick(vq);
 150
 151         /* When host has read buffer, this completes via balloon_ack */
 152         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 153
 154 }
 155
 156 static void set_page_pfns(struct virtio_balloon *vb,
 157                           __virtio32 pfns[], struct page *page)
 158 {
 159         unsigned int i;
 160
 161         /*
 162          * Set balloon pfns pointing at this page.
 163          * Note that the first pfn points at start of the page.
 164          */
 165         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 166                 pfns[i] = cpu_to_virtio32(vb->vdev,
 167                                           page_to_balloon_pfn(page) + i);
 168 }
 169
 170 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 171 {
 172         unsigned num_allocated_pages;
 173         unsigned num_pfns;
 174         struct page *page;
 175         LIST_HEAD(pages);
 176
 177         /* We can only do one array worth at a time. */
 178         num = min(num, ARRAY_SIZE(vb->pfns));
 179
 180         for (num_pfns = 0; num_pfns < num;
 181              num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 182                 struct page *page = balloon_page_alloc();
 183
 184                 if (!page) {
 185                         dev_info_ratelimited(&vb->vdev->dev,
 186                                              "Out of puff! Can't get %u pages\n",
 187                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 188                         /* Sleep for at least 1/5 of a second before retry. */
 189                         msleep(200);
 190                         break;
 191                 }
 192
 193                 balloon_page_push(&pages, page);
 194         }
 195
 196         mutex_lock(&vb->balloon_lock);
 197
 198         vb->num_pfns = 0;
 199
 200         while ((page = balloon_page_pop(&pages))) {
 201                 balloon_page_enqueue(&vb->vb_dev_info, page);
 202
 203                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 204                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 205                 if (!virtio_has_feature(vb->vdev,
 206                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 207                         adjust_managed_page_count(page, -1);
 208                 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
 209         }
 210
 211         num_allocated_pages = vb->num_pfns;
 212         /* Did we get any? */
 213         if (vb->num_pfns != 0)
 214                 tell_host(vb, vb->inflate_vq);
 215         mutex_unlock(&vb->balloon_lock);
 216
 217         return num_allocated_pages;
 218 }
 219
 220 static void release_pages_balloon(struct virtio_balloon *vb,
 221                                  struct list_head *pages)
 222 {
 223         struct page *page, *next;
 224
 225         list_for_each_entry_safe(page, next, pages, lru) {
 226                 if (!virtio_has_feature(vb->vdev,
 227                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 228                         adjust_managed_page_count(page, 1);
 229                 list_del(&page->lru);
 230                 put_page(page); /* balloon reference */
 231         }
 232 }
 233
 234 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 235 {
 236         unsigned num_freed_pages;
 237         struct page *page;
 238         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 239         LIST_HEAD(pages);
 240
 241         /* We can only do one array worth at a time. */
 242         num = min(num, ARRAY_SIZE(vb->pfns));
 243
 244         mutex_lock(&vb->balloon_lock);
 245         /* We can't release more pages than taken */
 246         num = min(num, (size_t)vb->num_pages);
 247         for (vb->num_pfns = 0; vb->num_pfns < num;
 248              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 249                 page = balloon_page_dequeue(vb_dev_info);
 250                 if (!page)
 251                         break;
 252                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 253                 list_add(&page->lru, &pages);
 254                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 255         }
 256
 257         num_freed_pages = vb->num_pfns;
 258         /*
 259          * Note that if
 260          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 261          * is true, we *have* to do it in this order
 262          */
 263         if (vb->num_pfns != 0)
 264                 tell_host(vb, vb->deflate_vq);
 265         release_pages_balloon(vb, &pages);
 266         mutex_unlock(&vb->balloon_lock);
 267         return num_freed_pages;
 268 }
 269
 270 static inline void update_stat(struct virtio_balloon *vb, int idx,
 271                                u16 tag, u64 val)
 272 {
 273         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 274         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 275         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 276 }
 277
 278 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 279
 280 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 281 {
 282         unsigned long events[NR_VM_EVENT_ITEMS];
 283         struct sysinfo i;
 284         unsigned int idx = 0;
 285         long available;
 286         unsigned long caches;
 287
 288         all_vm_events(events);
 289         si_meminfo(&i);
 290
 291         available = si_mem_available();
 292         caches = global_node_page_state(NR_FILE_PAGES);
 293
 294 #ifdef CONFIG_VM_EVENT_COUNTERS
 295         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 296                                 pages_to_bytes(events[PSWPIN]));
 297         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 298                                 pages_to_bytes(events[PSWPOUT]));
 299         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 300         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 301 #ifdef CONFIG_HUGETLB_PAGE
 302         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
 303                     events[HTLB_BUDDY_PGALLOC]);
 304         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
 305                     events[HTLB_BUDDY_PGALLOC_FAIL]);
 306 #endif
 307 #endif
 308         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 309                                 pages_to_bytes(i.freeram));
 310         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 311                                 pages_to_bytes(i.totalram));
 312         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
 313                                 pages_to_bytes(available));
 314         update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
 315                                 pages_to_bytes(caches));
 316
 317         return idx;
 318 }
 319
 320 /*
 321  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 322  * the stats queue operates in reverse.  The driver initializes the virtqueue
 323  * with a single buffer.  From that point forward, all conversations consist of
 324  * a hypervisor request (a call to this function) which directs us to refill
 325  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 326  * we delegate the job to a freezable workqueue that will do the actual work via
 327  * stats_handle_request().
 328  */
 329 static void stats_request(struct virtqueue *vq)
 330 {
 331         struct virtio_balloon *vb = vq->vdev->priv;
 332
 333         spin_lock(&vb->stop_update_lock);
 334         if (!vb->stop_update)
 335                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
 336         spin_unlock(&vb->stop_update_lock);
 337 }
 338
 339 static void stats_handle_request(struct virtio_balloon *vb)
 340 {
 341         struct virtqueue *vq;
 342         struct scatterlist sg;
 343         unsigned int len, num_stats;
 344
 345         num_stats = update_balloon_stats(vb);
 346
 347         vq = vb->stats_vq;
 348         if (!virtqueue_get_buf(vq, &len))
 349                 return;
 350         sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 351         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 352         virtqueue_kick(vq);
 353 }
 354
 355 static inline s64 towards_target(struct virtio_balloon *vb)
 356 {
 357         s64 target;
 358         u32 num_pages;
 359
 360         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
 361                      &num_pages);
 362
 363         /* Legacy balloon config space is LE, unlike all other devices. */
 364         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 365                 num_pages = le32_to_cpu((__force __le32)num_pages);
 366
 367         target = num_pages;
 368         return target - vb->num_pages;
 369 }
 370
 371 /* Gives back @num_to_return blocks of free pages to mm. */
 372 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
 373                                              unsigned long num_to_return)
 374 {
 375         struct page *page;
 376         unsigned long num_returned;
 377
 378         spin_lock_irq(&vb->free_page_list_lock);
 379         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
 380                 page = balloon_page_pop(&vb->free_page_list);
 381                 if (!page)
 382                         break;
 383                 free_pages((unsigned long)page_address(page),
 384                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 385         }
 386         vb->num_free_page_blocks -= num_returned;
 387         spin_unlock_irq(&vb->free_page_list_lock);
 388
 389         return num_returned;
 390 }
 391
 392 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
 393 {
 394         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 395                 return;
 396
 397         /* No need to queue the work if the bit was already set. */
 398         if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 399                              &vb->config_read_bitmap))
 400                 return;
 401
 402         queue_work(vb->balloon_wq, &vb->report_free_page_work);
 403 }
 404
 405 static void virtballoon_changed(struct virtio_device *vdev)
 406 {
 407         struct virtio_balloon *vb = vdev->priv;
 408         unsigned long flags;
 409
 410         spin_lock_irqsave(&vb->stop_update_lock, flags);
 411         if (!vb->stop_update) {
 412                 queue_work(system_freezable_wq,
 413                            &vb->update_balloon_size_work);
 414                 virtio_balloon_queue_free_page_work(vb);
 415         }
 416         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 417 }
 418
 419 static void update_balloon_size(struct virtio_balloon *vb)
 420 {
 421         u32 actual = vb->num_pages;
 422
 423         /* Legacy balloon config space is LE, unlike all other devices. */
 424         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 425                 actual = (__force u32)cpu_to_le32(actual);
 426
 427         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
 428                       &actual);
 429 }
 430
 431 static void update_balloon_stats_func(struct work_struct *work)
 432 {
 433         struct virtio_balloon *vb;
 434
 435         vb = container_of(work, struct virtio_balloon,
 436                           update_balloon_stats_work);
 437         stats_handle_request(vb);
 438 }
 439
 440 static void update_balloon_size_func(struct work_struct *work)
 441 {
 442         struct virtio_balloon *vb;
 443         s64 diff;
 444
 445         vb = container_of(work, struct virtio_balloon,
 446                           update_balloon_size_work);
 447         diff = towards_target(vb);
 448
 449         if (!diff)
 450                 return;
 451
 452         if (diff > 0)
 453                 diff -= fill_balloon(vb, diff);
 454         else
 455                 diff += leak_balloon(vb, -diff);
 456         update_balloon_size(vb);
 457
 458         if (diff)
 459                 queue_work(system_freezable_wq, work);
 460 }
 461
 462 static int init_vqs(struct virtio_balloon *vb)
 463 {
 464         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
 465         vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
 466         const char *names[VIRTIO_BALLOON_VQ_MAX];
 467         int err;
 468
 469         /*
 470          * Inflateq and deflateq are used unconditionally. The names[]
 471          * will be NULL if the related feature is not enabled, which will
 472          * cause no allocation for the corresponding virtqueue in find_vqs.
 473          */
 474         callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
 475         names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
 476         callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
 477         names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
 478         names[VIRTIO_BALLOON_VQ_STATS] = NULL;
 479         names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 480
 481         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 482                 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
 483                 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
 484         }
 485
 486         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 487                 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
 488                 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 489         }
 490
 491         err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
 492                                          vqs, callbacks, names, NULL, NULL);
 493         if (err)
 494                 return err;
 495
 496         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
 497         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 498         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 499                 struct scatterlist sg;
 500                 unsigned int num_stats;
 501                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
 502
 503                 /*
 504                  * Prime this virtqueue with one buffer so the hypervisor can
 505                  * use it to signal us later (it can't be broken yet!).
 506                  */
 507                 num_stats = update_balloon_stats(vb);
 508
 509                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 510                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
 511                                            GFP_KERNEL);
 512                 if (err) {
 513                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
 514                                  __func__);
 515                         return err;
 516                 }
 517                 virtqueue_kick(vb->stats_vq);
 518         }
 519
 520         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 521                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
 522
 523         return 0;
 524 }
 525
 526 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
 527 {
 528         if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 529                                &vb->config_read_bitmap))
 530                 virtio_cread(vb->vdev, struct virtio_balloon_config,
 531                              free_page_report_cmd_id,
 532                              &vb->cmd_id_received_cache);
 533
 534         return vb->cmd_id_received_cache;
 535 }
 536
 537 static int send_cmd_id_start(struct virtio_balloon *vb)
 538 {
 539         struct scatterlist sg;
 540         struct virtqueue *vq = vb->free_page_vq;
 541         int err, unused;
 542
 543         /* Detach all the used buffers from the vq */
 544         while (virtqueue_get_buf(vq, &unused))
 545                 ;
 546
 547         vb->cmd_id_active = virtio32_to_cpu(vb->vdev,
 548                                         virtio_balloon_cmd_id_received(vb));
 549         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
 550         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
 551         if (!err)
 552                 virtqueue_kick(vq);
 553         return err;
 554 }
 555
 556 static int send_cmd_id_stop(struct virtio_balloon *vb)
 557 {
 558         struct scatterlist sg;
 559         struct virtqueue *vq = vb->free_page_vq;
 560         int err, unused;
 561
 562         /* Detach all the used buffers from the vq */
 563         while (virtqueue_get_buf(vq, &unused))
 564                 ;
 565
 566         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
 567         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
 568         if (!err)
 569                 virtqueue_kick(vq);
 570         return err;
 571 }
 572
 573 static int get_free_page_and_send(struct virtio_balloon *vb)
 574 {
 575         struct virtqueue *vq = vb->free_page_vq;
 576         struct page *page;
 577         struct scatterlist sg;
 578         int err, unused;
 579         void *p;
 580
 581         /* Detach all the used buffers from the vq */
 582         while (virtqueue_get_buf(vq, &unused))
 583                 ;
 584
 585         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
 586                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 587         /*
 588          * When the allocation returns NULL, it indicates that we have got all
 589          * the possible free pages, so return -EINTR to stop.
 590          */
 591         if (!page)
 592                 return -EINTR;
 593
 594         p = page_address(page);
 595         sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
 596         /* There is always 1 entry reserved for the cmd id to use. */
 597         if (vq->num_free > 1) {
 598                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
 599                 if (unlikely(err)) {
 600                         free_pages((unsigned long)p,
 601                                    VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 602                         return err;
 603                 }
 604                 virtqueue_kick(vq);
 605                 spin_lock_irq(&vb->free_page_list_lock);
 606                 balloon_page_push(&vb->free_page_list, page);
 607                 vb->num_free_page_blocks++;
 608                 spin_unlock_irq(&vb->free_page_list_lock);
 609         } else {
 610                 /*
 611                  * The vq has no available entry to add this page block, so
 612                  * just free it.
 613                  */
 614                 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 615         }
 616
 617         return 0;
 618 }
 619
 620 static int send_free_pages(struct virtio_balloon *vb)
 621 {
 622         int err;
 623         u32 cmd_id_active;
 624
 625         while (1) {
 626                 /*
 627                  * If a stop id or a new cmd id was just received from host,
 628                  * stop the reporting.
 629                  */
 630                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
 631                 if (unlikely(cmd_id_active !=
 632                              virtio_balloon_cmd_id_received(vb)))
 633                         break;
 634
 635                 /*
 636                  * The free page blocks are allocated and sent to host one by
 637                  * one.
 638                  */
 639                 err = get_free_page_and_send(vb);
 640                 if (err == -EINTR)
 641                         break;
 642                 else if (unlikely(err))
 643                         return err;
 644         }
 645
 646         return 0;
 647 }
 648
 649 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
 650 {
 651         int err;
 652         struct device *dev = &vb->vdev->dev;
 653
 654         /* Start by sending the received cmd id to host with an outbuf. */
 655         err = send_cmd_id_start(vb);
 656         if (unlikely(err))
 657                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
 658
 659         err = send_free_pages(vb);
 660         if (unlikely(err))
 661                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
 662
 663         /* End by sending a stop id to host with an outbuf. */
 664         err = send_cmd_id_stop(vb);
 665         if (unlikely(err))
 666                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
 667 }
 668
 669 static void report_free_page_func(struct work_struct *work)
 670 {
 671         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
 672                                                  report_free_page_work);
 673         u32 cmd_id_received;
 674
 675         cmd_id_received = virtio_balloon_cmd_id_received(vb);
 676         if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
 677                 /* Pass ULONG_MAX to give back all the free pages */
 678                 return_free_pages_to_mm(vb, ULONG_MAX);
 679         } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
 680                    cmd_id_received !=
 681                    virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
 682                 virtio_balloon_report_free_page(vb);
 683         }
 684 }
 685
 686 #ifdef CONFIG_BALLOON_COMPACTION
 687 /*
 688  * virtballoon_migratepage - perform the balloon page migration on behalf of
 689  *                           a compation thread.     (called under page lock)
 690  * @vb_dev_info: the balloon device
 691  * @newpage: page that will replace the isolated page after migration finishes.
 692  * @page   : the isolated (old) page that is about to be migrated to newpage.
 693  * @mode   : compaction mode -- not used for balloon page migration.
 694  *
 695  * After a ballooned page gets isolated by compaction procedures, this is the
 696  * function that performs the page migration on behalf of a compaction thread
 697  * The page migration for virtio balloon is done in a simple swap fashion which
 698  * follows these two macro steps:
 699  *  1) insert newpage into vb->pages list and update the host about it;
 700  *  2) update the host about the old page removed from vb->pages list;
 701  *
 702  * This function preforms the balloon page migration task.
 703  * Called through balloon_mapping->a_ops->migratepage
 704  */
 705 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 706                 struct page *newpage, struct page *page, enum migrate_mode mode)
 707 {
 708         struct virtio_balloon *vb = container_of(vb_dev_info,
 709                         struct virtio_balloon, vb_dev_info);
 710         unsigned long flags;
 711
 712         /*
 713          * In order to avoid lock contention while migrating pages concurrently
 714          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 715          * this turn, as it is easier to retry the page migration later.
 716          * This also prevents fill_balloon() getting stuck into a mutex
 717          * recursion in the case it ends up triggering memory compaction
 718          * while it is attempting to inflate the ballon.
 719          */
 720         if (!mutex_trylock(&vb->balloon_lock))
 721                 return -EAGAIN;
 722
 723         get_page(newpage); /* balloon reference */
 724
 725         /*
 726           * When we migrate a page to a different zone and adjusted the
 727           * managed page count when inflating, we have to fixup the count of
 728           * both involved zones.
 729           */
 730         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
 731             page_zone(page) != page_zone(newpage)) {
 732                 adjust_managed_page_count(page, 1);
 733                 adjust_managed_page_count(newpage, -1);
 734         }
 735
 736         /* balloon's page migration 1st step  -- inflate "newpage" */
 737         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 738         balloon_page_insert(vb_dev_info, newpage);
 739         vb_dev_info->isolated_pages--;
 740         __count_vm_event(BALLOON_MIGRATE);
 741         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 742         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 743         set_page_pfns(vb, vb->pfns, newpage);
 744         tell_host(vb, vb->inflate_vq);
 745
 746         /* balloon's page migration 2nd step -- deflate "page" */
 747         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 748         balloon_page_delete(page);
 749         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 750         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 751         set_page_pfns(vb, vb->pfns, page);
 752         tell_host(vb, vb->deflate_vq);
 753
 754         mutex_unlock(&vb->balloon_lock);
 755
 756         put_page(page); /* balloon reference */
 757
 758         return MIGRATEPAGE_SUCCESS;
 759 }
 760
 761 static int balloon_init_fs_context(struct fs_context *fc)
 762 {
 763         return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
 764 }
 765
 766 static struct file_system_type balloon_fs = {
 767         .name           = "balloon-kvm",
 768         .init_fs_context = balloon_init_fs_context,
 769         .kill_sb        = kill_anon_super,
 770 };
 771
 772 #endif /* CONFIG_BALLOON_COMPACTION */
 773
 774 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
 775                                        unsigned long pages_to_free)
 776 {
 777         unsigned long blocks_to_free, blocks_freed;
 778
 779         pages_to_free = round_up(pages_to_free,
 780                                  VIRTIO_BALLOON_HINT_BLOCK_PAGES);
 781         blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 782         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
 783
 784         return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 785 }
 786
 787 static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
 788                                           unsigned long pages_to_free)
 789 {
 790         return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) /
 791                 VIRTIO_BALLOON_PAGES_PER_PAGE;
 792 }
 793
 794 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
 795                                           unsigned long pages_to_free)
 796 {
 797         unsigned long pages_freed = 0;
 798
 799         /*
 800          * One invocation of leak_balloon can deflate at most
 801          * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
 802          * multiple times to deflate pages till reaching pages_to_free.
 803          */
 804         while (vb->num_pages && pages_freed < pages_to_free)
 805                 pages_freed += leak_balloon_pages(vb,
 806                                                   pages_to_free - pages_freed);
 807
 808         update_balloon_size(vb);
 809
 810         return pages_freed;
 811 }
 812
 813 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
 814                                                   struct shrink_control *sc)
 815 {
 816         unsigned long pages_to_free, pages_freed = 0;
 817         struct virtio_balloon *vb = container_of(shrinker,
 818                                         struct virtio_balloon, shrinker);
 819
 820         pages_to_free = sc->nr_to_scan;
 821
 822         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 823                 pages_freed = shrink_free_pages(vb, pages_to_free);
 824
 825         if (pages_freed >= pages_to_free)
 826                 return pages_freed;
 827
 828         pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
 829
 830         return pages_freed;
 831 }
 832
 833 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
 834                                                    struct shrink_control *sc)
 835 {
 836         struct virtio_balloon *vb = container_of(shrinker,
 837                                         struct virtio_balloon, shrinker);
 838         unsigned long count;
 839
 840         count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
 841         count += vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 842
 843         return count;
 844 }
 845
 846 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
 847 {
 848         unregister_shrinker(&vb->shrinker);
 849 }
 850
 851 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 852 {
 853         vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
 854         vb->shrinker.count_objects = virtio_balloon_shrinker_count;
 855         vb->shrinker.seeks = DEFAULT_SEEKS;
 856
 857         return register_shrinker(&vb->shrinker);
 858 }
 859
 860 static int virtballoon_probe(struct virtio_device *vdev)
 861 {
 862         struct virtio_balloon *vb;
 863         __u32 poison_val;
 864         int err;
 865
 866         if (!vdev->config->get) {
 867                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 868                         __func__);
 869                 return -EINVAL;
 870         }
 871
 872         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
 873         if (!vb) {
 874                 err = -ENOMEM;
 875                 goto out;
 876         }
 877
 878         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 879         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 880         spin_lock_init(&vb->stop_update_lock);
 881         mutex_init(&vb->balloon_lock);
 882         init_waitqueue_head(&vb->acked);
 883         vb->vdev = vdev;
 884
 885         balloon_devinfo_init(&vb->vb_dev_info);
 886
 887         err = init_vqs(vb);
 888         if (err)
 889                 goto out_free_vb;
 890
 891 #ifdef CONFIG_BALLOON_COMPACTION
 892         balloon_mnt = kern_mount(&balloon_fs);
 893         if (IS_ERR(balloon_mnt)) {
 894                 err = PTR_ERR(balloon_mnt);
 895                 goto out_del_vqs;
 896         }
 897
 898         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 899         vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
 900         if (IS_ERR(vb->vb_dev_info.inode)) {
 901                 err = PTR_ERR(vb->vb_dev_info.inode);
 902                 kern_unmount(balloon_mnt);
 903                 goto out_del_vqs;
 904         }
 905         vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
 906 #endif
 907         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 908                 /*
 909                  * There is always one entry reserved for cmd id, so the ring
 910                  * size needs to be at least two to report free page hints.
 911                  */
 912                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
 913                         err = -ENOSPC;
 914                         goto out_del_vqs;
 915                 }
 916                 vb->balloon_wq = alloc_workqueue("balloon-wq",
 917                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 918                 if (!vb->balloon_wq) {
 919                         err = -ENOMEM;
 920                         goto out_del_vqs;
 921                 }
 922                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
 923                 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
 924                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 925                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 926                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
 927                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 928                 spin_lock_init(&vb->free_page_list_lock);
 929                 INIT_LIST_HEAD(&vb->free_page_list);
 930                 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
 931                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
 932                         virtio_cwrite(vb->vdev, struct virtio_balloon_config,
 933                                       poison_val, &poison_val);
 934                 }
 935         }
 936         /*
 937          * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
 938          * shrinker needs to be registered to relieve memory pressure.
 939          */
 940         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
 941                 err = virtio_balloon_register_shrinker(vb);
 942                 if (err)
 943                         goto out_del_balloon_wq;
 944         }
 945         virtio_device_ready(vdev);
 946
 947         if (towards_target(vb))
 948                 virtballoon_changed(vdev);
 949         return 0;
 950
 951 out_del_balloon_wq:
 952         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 953                 destroy_workqueue(vb->balloon_wq);
 954 out_del_vqs:
 955         vdev->config->del_vqs(vdev);
 956 out_free_vb:
 957         kfree(vb);
 958 out:
 959         return err;
 960 }
 961
 962 static void remove_common(struct virtio_balloon *vb)
 963 {
 964         /* There might be pages left in the balloon: free them. */
 965         while (vb->num_pages)
 966                 leak_balloon(vb, vb->num_pages);
 967         update_balloon_size(vb);
 968
 969         /* Now we reset the device so we can clean up the queues. */
 970         vb->vdev->config->reset(vb->vdev);
 971
 972         vb->vdev->config->del_vqs(vb->vdev);
 973 }
 974
 975 static void virtballoon_remove(struct virtio_device *vdev)
 976 {
 977         struct virtio_balloon *vb = vdev->priv;
 978
 979         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 980                 virtio_balloon_unregister_shrinker(vb);
 981         spin_lock_irq(&vb->stop_update_lock);
 982         vb->stop_update = true;
 983         spin_unlock_irq(&vb->stop_update_lock);
 984         cancel_work_sync(&vb->update_balloon_size_work);
 985         cancel_work_sync(&vb->update_balloon_stats_work);
 986
 987         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 988                 cancel_work_sync(&vb->report_free_page_work);
 989                 destroy_workqueue(vb->balloon_wq);
 990         }
 991
 992         remove_common(vb);
 993 #ifdef CONFIG_BALLOON_COMPACTION
 994         if (vb->vb_dev_info.inode)
 995                 iput(vb->vb_dev_info.inode);
 996
 997         kern_unmount(balloon_mnt);
 998 #endif
 999         kfree(vb);
1000 }
1001
1002 #ifdef CONFIG_PM_SLEEP
1003 static int virtballoon_freeze(struct virtio_device *vdev)
1004 {
1005         struct virtio_balloon *vb = vdev->priv;
1006
1007         /*
1008          * The workqueue is already frozen by the PM core before this
1009          * function is called.
1010          */
1011         remove_common(vb);
1012         return 0;
1013 }
1014
1015 static int virtballoon_restore(struct virtio_device *vdev)
1016 {
1017         struct virtio_balloon *vb = vdev->priv;
1018         int ret;
1019
1020         ret = init_vqs(vdev->priv);
1021         if (ret)
1022                 return ret;
1023
1024         virtio_device_ready(vdev);
1025
1026         if (towards_target(vb))
1027                 virtballoon_changed(vdev);
1028         update_balloon_size(vb);
1029         return 0;
1030 }
1031 #endif
1032
1033 static int virtballoon_validate(struct virtio_device *vdev)
1034 {
1035         if (!page_poisoning_enabled())
1036                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1037
1038         __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1039         return 0;
1040 }
1041
1042 static unsigned int features[] = {
1043         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1044         VIRTIO_BALLOON_F_STATS_VQ,
1045         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1046         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1047         VIRTIO_BALLOON_F_PAGE_POISON,
1048 };
1049
1050 static struct virtio_driver virtio_balloon_driver = {
1051         .feature_table = features,
1052         .feature_table_size = ARRAY_SIZE(features),
1053         .driver.name =  KBUILD_MODNAME,
1054         .driver.owner = THIS_MODULE,
1055         .id_table =     id_table,
1056         .validate =     virtballoon_validate,
1057         .probe =        virtballoon_probe,
1058         .remove =       virtballoon_remove,
1059         .config_changed = virtballoon_changed,
1060 #ifdef CONFIG_PM_SLEEP
1061         .freeze =       virtballoon_freeze,
1062         .restore =      virtballoon_restore,
1063 #endif
1064 };
1065
1066 module_virtio_driver(virtio_balloon_driver);
1067 MODULE_DEVICE_TABLE(virtio, id_table);
1068 MODULE_DESCRIPTION("Virtio balloon driver");
1069 MODULE_LICENSE("GPL");